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S D Carlson

Publications and source records attributed to S D Carlson.

At least 37 records · Page 2Linked to original sources
PubMed1981

Lanthanum and freeze fracture studies on the retinular cell junction in the compound eye of the housefly.

The retinular (R) cell junction between adjacent photoreceptor cells in the house-fly ommatidium was characterized by freeze fracture, thin section and tracer (lanthanum) studies. Focal tight junctions occur between cells, and some P face ridge-E face groove correspondences are present in this intramembranal area. When colloidal lanthanum was introduced into the extracellular space (ECS) of the peripheral retina of the housefly, this electron-dense tracer moved from the ECS (extra-ommatidial space), through the R-cell junctions and belt desmosomes, into the ommatidial cavity (OC = intrarhabdomal space) of each ommatidium. In the OC, lanthanum outlined a meshwork structure that pervaded this space. The evidence of this tracer movement suggests that there may be ionic continuity between the "traditional" ECS and the fluid bathing the individual rhabdomeres. The volume of the OC is calculated and we suggest that this space is part of the ECS. The functional implications of this postulate are considered in the light of: (1) the different functions of the peripheral and central cells; (2) the dissimilarity of rhabdomal membrane surface facing the OC compared to the "unmodified" plasma membrane of the photoreceptor cell facing the extra-ommatidial cavity; (3) the permeability properties of the R cell junction; and (4) the total ECS containing an ion store capable of sustaining current for the generator potential.

Animals↗
PubMed1981

The perineurium of the adult housefly: ultrastructure and permeability to lanthanum.

The ultrastructure of the perineurial cells of Musca overlying the first optic neuropile was examined by transmission electron microscopy. These cells are somewhat similar to those of other insects but cytoplasmic flanges seem to be absent, and mitochondria are relatively large and sinuous. The intercellular channel system on the lateral border of the cells is relatively spacious and highly meandering. Perineurial cells are joined by septate, gap, and tight junctions, hemidesmosomes, and desmosomes. Tight and septate junctions bond perineurial cells and glial cells. These data are evaluated on the basis of tracer studies with lanthanum. This material penetrates the extracellular space between perineurium and underlying glial and nerve cells, between epithelial glial cells and retinular axon terminals (capitate projections), and between the alpha-beta fiber pair in the optic cartridge (gnarls). If no damage occurs to the perineurial cells during tissue preparation, this passage of lanthanum to neuronal surfaces indicates that the blood brain barrier is incomplete in this restricted area. Supportive evidence for such permeance is based on electrophysiological data, considerations of membrane specializations in the optic neuropile, and Na+/K+ ratios of dipteran hemolymph.

Animals↗
PubMed1980

Membrane specializations in the first optic neuropil of the housefly, Musca domestica L. I. Junctions between neurons.

Thin section and freeze-fracture replicas of the first optic neuropil (lamina ganglionaris) of the fly Musca were studied to determine the types, extent and location of membrane specializations between neurons. Five junctional types are found, exclusive of chemical synapses. These are gap, tight and septate junctions, close appositions between retinular (R) axons and capitate projections (in which an epithelial glial cell invaginates into an R axon). Junctional types and their cellular associations follow: gap junctions, between lamina (L) interneurons, L1-L2; tight junctions, between L1-L2; L3-L4; L4-epithelial glial cell; and R7-R8. Septate junctions, between L1-L2, L3-L4, L3-beta, L4-beta, alpha-beta, and an unidentified fibre making septate junctions with L1 and L2. Close appositions are found between R axons in the distal portion of the optic cartridges of this neuropil prior to extensive R chemical synapses with L1, L2. These loci (seen in freeze-fracture replicas) have rhomboidal patches of hexagonally arrayed P face particles. Intermembranous clefts between R axons are about 50 A and are invariably electron lucent. These points of near contact between R terminals are probably the sites of low electrical resistance measured by Shaw (1979). Capitate projections are for the first time revealed in freeze fracture surfaces. Here epithelial glia send many, short, mushroom-shaped processes invaginating into R axons forming a tenacious structural bond. All four membrane leaflets (P and E faces of R axon and glial membrane) in the capitate projection possess particles in higher densities than in the surrounding nonspecialized regions. The known, general functions of each membrane specialization were correlated with the functional capacities of those lamina neurons possessing them in an effort to interpret better the integrative capacity of this neuropil. These data provide some fine structural bases for a putative 'blood-brain' barrier between lamina and haemolymph, between lamina and peripheral retina, and possibly between lamina and second optic neuropil.

Animals↗
PubMed1980

Membrane specializations in the first optic neuropil of the housefly, Musca domestica L. II. Junctions between glial cells.

Membrane specializations between the three types of glial cells in the first optic neuropil (lamina ganglionaris) of the housefly were determined from thin sections and freeze-fracture replicas. Three strata of glia cells are present in the lamina. A relatively thin layer of satellite glia covers the distal (perikaryal) rind of the lamina and these cells wrap retinular axons that enter the lamina. The central synaptic fields of the lamina neurons are enclosed by epithelial glia, while the proximal surface of the lamina is capped by marginal glial cells. Satellite glia bond to each other via desmosomes, septate and gap junctions. Freeze-fracture replicas show gap junctions as aggregations of E face particles and P face pits on the intramembranous surfaces. Parallel rows of P face particles are indicative of septate junctions. Angulated, intersecting, P face particle ridges are arranged in circumferential bands around retinular axons at the glia-axon interface. Thin section correlates of these junctions are presented. Epithelial glia are characterized by elaborate series of parallel membranes which appear to be suspended in the cytoplasm but may be the invaginated plasma membranes of a neighbouring glial cell. An intermembranous cleft of 40-50 A is noted and this area has an appreciable electron density which give the appearance of a gap junction. When cleaved, these membranes show plaques of particles on the P face. The marginal glial cells are relatively large and are joined by a newly discovered junction which is characterized (from freeze-fracture data) by numerous, undulating, uninterrupted, parallel P face ridges which sometimes become circular and form enclosures. In thin section, electron-dense material fills the membrane appositional areas and in tangential sections faint diffuse parallel striae are seen. This specialized cell contact may be a variant of a continuous junction although, based on fracture replicas, there are obvious similarities to tight junctions. These membranes specializations are related, in the three dimensions of the optic cartridges, to functions in a possible blood-eye barrier system.

Animals↗
PubMed1977

Effect of dietary egg on serum cholesterol and triglyceride of human males.

One hundred fourteen male volunteers (mean age 44.6 years) consumed one whole egg daily in their customary diets for 3 months. Their final serum cholesterol (SCHOL) and triglycerides (STG) levels were compared with their initial levels on customary free choice diets and also with their levels after a 3-month elimination of dietary whole eggs. All subjects had previously confirmed normal serum lipid levels and no history of heart disease. Four-day food records were kept during both experimental dietary periods. A Latin square design allowed analysis for seasonal effects on lipid levels. No significant change in mean SCHOL on either diet was found; there was a seasonal effect on mean STG. Significant linear associations of fat intake and of energy intake were found. There was no significant association of dietary cholesterol intake with either SCHOL or STG.

Adult↗
PubMed1976

The large pigment cell of the compound eye of the house fly Musca domestica. Fine structure and cytoarchitectural associations.

The fine structure and cellular associations of the large pigment cells (LPC's) of the compound eye of the house fly were studied with high voltage and conventional electron microscopy. Depending on the sector of the compound eye, the facets are either rectangular or hexagonal. The underside of each facet has indentations exactly aligned with those on top into which inserts an angulated sleeve of LPC's. Under the rectangular lens facet 6 or 8 small compact (in cross section) LPC's join four elongate LPC's. Clusters of compact cells alternate in this ring with elongate ones. Compact cells compress together and become quadrangular (in cross section) several microns below their insertion into the lens and form "building block" corners while elongate cells form "side rails" for the rectangular type of distal pseudocone enclosure. Beneath hexagonal facets all LPC's are rather elongate with out corner cells. In both facet types LPC's enclose the pseudocone for a longitudinal distance of 4 mum and then are displaced as bordering cells by a sleeve of two corneal pigment cells (CPC's), each of which encloses half of the proximal pseudocone. For the following 6 mum of longitudinal distance these concentric sleeves of CPC's and LPC's form a double layer around the pseudocone. At about 10 mum below lens base the two sleeves separate; LPC's become attenuated and extend cable-like to the basement membrane and CPC's enclose the proximal pseudocone, Semper cells and distal retinula. The junction between lens and LPC's has critical structural value in that (1) this is the sole anchorage to the lens by the lengthy remainder of the ommatidium, and (2) LPC's enclose the semiliquid pseudocone in the most distal portion of the pseudocone. In addition to vertical support, the LPC's send out numerous lateral processes that make structural contact among themselves, with the corneal pigment cells and the photoreceptor cells. The structural features of this array are discussed relative to possible physiological roles.

Animals↗
PubMed1976

High voltage electron microscopy of the optic neuropile of the housefly, Musca domestica.

Synaptic cartridges of the first optic neuropile (lamina ganglionaris) of the housefly were examined by high voltage electron microscopy (HVEM). Stereo pairs (from thick, i.e., 0.25 mum, sections viewed at 1,000 kV) provided a three dimensional representation of cartridge neurons and clearly revealed the lateral spread, bifurcation and some functional associations of Type I (L1, L2) monopolar interneurons. Slightly proximal to cartridge neck level, pairs of retinular (R) axons made contact with each other and it appeared that R processes projected through the cleft between the Type I interneurons. No junctional modifications were seen between contiguous R axon terminals. The speculation was made that functional contact might exist between neighboring R axons prior to their extensive synapses with principal first order interneurons. Such alleged coupling between R axons would account for several electrophysiological findings from other laboratories. Modifications in EM technique applicable for HVEM were detailed. The value of obtaining thick serial sections and the use of the HVEM in expediting three dimensional reconstructions of neuropile were demonstrated.

Animals↗
PubMed1976

The housefly interfacetal hair: ultrastructure of a presumed mechanoreceptor.

The external and internal fine structure of the housefly interfacetal hair and its sensory dendrite was studied with the scanning and transmission (high and low voltage) electron microscopes. The hair shaft contains no dendrites, and is usually situated within a socket on the lens surface. Immediately beneath and directly connected to the base of each hair is a bipolar neuron whose dendrite tip is enveloped in a shealth cell which, in turn, is surrounded by a second sheath cell. Septate junctions are seen between all these cells and contiguous portions of a large pigment cell. At the hair base, the dendrite of the neuron terminates in a tubular body only 1.5 mum in diameter which is filled with about 400 microtubules in highly ordered (in parallel pentagonal and hexagonal) arrays and whose sides are fused to neurofilaments in parallel. Another filament (ca. 70 A diameter) is in the center of each microtubule-neurofilament polygon. Structures proximal to the tubular body are typical for a scolopoid sensillum, i.e., connecting cilium (9 times 2 + 0 microtubules) with rootlet and basal bodies, unmodified dendrite, perikaryon and axon. The axon has not been traced to its synapse. The high degree of internal organization and shortness of the tubular body, as well as its eccentric insertion into the hair shaft lead to the hypothesis that this hair may be a highly sensitive mechanoreceptor. On the basis of their single innervation, these hairs could monitor flight speed from the degree of hair deflection caused by wind in general or particular laminar air currents flowing past the eyes during flight.

Air Movements↗
PubMed1976

Scanning electron microscopy of normal and malignant human urothelium.

Scanning electron microscopy (SEM) was used to evaluate and compare normal bladder mucosa to tumor epithelium as well as to normal-appearing mucosa in patients with diagnosed bladder tumor. Bladder urothelium adjacent to tumors exhibits a characteristic pattern of fine structural relief which is distinct from normal uroepithelium. These changes in microcontour may be guides to the identification of early malignancy, and thus the technique will be helpful in deciding how aggressive the treatment of bladder tumor should be.

Aged↗
PubMed1975

Ultrastructure of the compound eye of the diploid female beetle, Xyleborus ferrugineus.

The compound eye of female (diploid) Xyleborus ferrugineus beetles was examined with scanning and transmission electron microscopy. The eye is emarginate, and externally consists of roughly 70-100 facets. Each ommatidium is composed of a thickly biconvex lenslet with about 50 electron dense and rare layers. The lens facet overlies a crystalline cone of the acone type which is roughly hourglass-shaped. Pigment cells envelop the entire ommatidium, and pigment granules also are abundant throughout the cytoplasm of the 8 retinular cells. The rhabdomeres of 2 centrally situated photoreceptor cells effectively fuse into a rhabdom that extends from the base of the crystalline cone deeply into the ommatidium. Six distal peripheral retinular cells encircle the 2 central cells, and their rhabdomeres join laterally to form a rhabdomeric ring around the central rhabdom. The rhabdom and rhabdomeric ring are effectively separated by the cytoplasm of the two central retinular cells which contains the usual organelles and an abundance of shielding pigment granules. Eight axons per ommatidium gather in a tracheae-less fascicle before exiting the eye through the fenestrate basement membrane. No tracheation was observed among the retinular cells. Each Semper cell of each observed crystalline cone contained an abundance of virus-like particles near the cell nucleus. The insect is laboratory reared, and the visual system seems very amenable to photoreceptor investigations.

Animals↗
PubMed1975

The distal ommatidium of the compound eye of the housefly (Musca domestica): a scanning electron microscope study.

The distal aspect of the housefly ommatidium was surveyed by the scanning electron microscope. Attention was directed to the somal eminence of the superior central cell and the lens to large pigment cell junction. The underside of each lens facet exhibits six hexagonally arranged incisures. Into each of these indentations are fitted several large pigment cells. This hexagonal indentation appears to be a tenacious anchorage. Two corneal pigment cells laterally encircle the pseudocone and at their proximal extension they enclose the Semper cells and neck of the retinula. The somal eminence of the superior central cell is about 10 mum from the base of the corneal pigment cell enclosure. Micrographs were used to construct a diagram of the ommatidium above the basement membrane. Suggestions are made as to the functional correlates of the observed ommatidial structures.

Animals↗